The proposed research is intended to further the study of the immune response by the analysis of well-defined immunologic systems. These systems include both the investigation of the immune response to haptenic determinants in vitro, and the application of such investigations to the study of homogeneous cell populations. Stimulation and analysis of monoclonal antibody producing cell cultures will be utilized to further characterize the precursor cells of primary and secondary antibody forming cells. Utilizing neonatal animals as donors of such precursor cells should allow an analysis of the development of immunologic specificity and competence. In addition, an analysis of the parameters of stimulation of primary and secondary clonal precursor cells should allow further clarification of the mechanism of antigenic stimulation both with regard to the specific interaction of antigens with responsive cells and the interactions of such cells with one another in the stimulatory process. Bibliographic references: The Regulation of Expression of B Cell Clones. Klinman, N.R. and Press, J.L. Immunogenetics 1:536, 1975; The Expression of Specific Clones During B Cell Development. Klinman, N.R. and Press, J.L. In the Symposium on Developmental Biology Fed. Proc. 34: 47, 1975.